How does commit 47ec340c not introduce a bug?

Haojian Zhuang
2013-05-07T09:35:28Z

On Tue, May 7, 2013 at 5:24 PM, Uwe Kleine-K?nig
<u.kleine-koenig@pengutronix.de> wrote:
> Hello,
>
> On Tue, May 07, 2013 at 04:17:34AM -0500, Robin Holt wrote:
>> I noticed a warning while cross-compiling all arm defconfigs.
>>
>> The mmp2_defconfig gave this warning:
>>
>> drivers/video/backlight/max8925_bl.c: In function 'max8925_backlight_probe':
>> drivers/video/backlight/max8925_bl.c:177:3: warning: statement with no effect [-Wunused-value]
>>
>> This appears to have been introduced by the above commit when !CONFIG_OF
>>
>> Looking at this more closely, I am not sure how this was ever intended
>> to be handled or how the errors returned in the CONFIG_OF case were
>> intended to be handled as the return from max8925_backlight_dt_init is
>> always ignored.
>>
>> I think this needs some more attention, but do not feel like I know
>> enough about it or have any means to test it to weigh in.
>>
>> Thanks,
>> Robin
>>
>>
>> commit 47ec340cb8e232671e7c4a4689ff32c3bdf329da
>> Author: Qing Xu <qingx@marvell.com>
>> Date: Mon Feb 4 23:40:45 2013 +0800
>>
>> mfd: max8925: Support dt for backlight
>>
>> Add device tree support in max8925 backlight.
>>
>> Signed-off-by: Qing Xu <qingx@marvell.com>
>> Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
>> Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
>>
>> diff --git a/drivers/video/backlight/max8925_bl.c b/drivers/video/backlight/max8925_bl.c
>> index 2c9bce0..5ca11b0 100644
>> --- a/drivers/video/backlight/max8925_bl.c
>> +++ b/drivers/video/backlight/max8925_bl.c
>> @@ -101,6 +101,29 @@ static const struct backlight_ops max8925_backlight_ops = {
>> .get_brightness = max8925_backlight_get_brightness,
>> };
>>
>> +#ifdef CONFIG_OF
>> +static int max8925_backlight_dt_init(struct platform_device *pdev,
>> + struct max8925_backlight_pdata *pdata)
>> +{
>> + struct device_node *nproot = pdev->dev.parent->of_node, *np;
>> + int dual_string;
>> +
>> + if (!nproot)
>> + return -ENODEV;
>> + np = of_find_node_by_name(nproot, "backlight");
>> + if (!np) {
>> + dev_err(&pdev->dev, "failed to find backlight node\n");
>> + return -ENODEV;
>> + }
>> +
>> + of_property_read_u32(np, "maxim,max8925-dual-string", &dual_string);
>> + pdata->dual_string = dual_string;
>> + return 0;
>> +}
>> +#else
>> +#define max8925_backlight_dt_init(x, y) (-1)
> It's probably best to make this:
>
> static inline max8925_backlight_dt_init(struct platform_device *pdev,
> struct max8925_backlight_pdata *pdata)
> {
> return -ENODEV;
> }
>

I've submitted this patch to fix this issue for a long time.

Samuel,

Should I send it again?

Regards
Haojian